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Abstract:

A letter written in 1710 by Robert, first Viscount Molesworth, to his wife describes
ongoing work to the garden of their estate in Co. Dublin and to the digging of ponds
and the subsequent making of bricks. This connection between the formation of
designed landscape and the production of brick for building purposes has prompted
the following scientific investigation. The paper applies physical science to the
study of eighteenth-century Irish brick in order to gather information about its
provenance and the source of its constituent materials. Analytical techniques were
employed to study the bricks used to build Arch Hall, a mansion house dating from
the first half of the eighteenth century with an extensive demesne in Co. Meath. Clay
samples were collected from the demesne, fired in the laboratory and analysed for
comparative purposes. The results indicate that the bricks are hand-made with silica-
based, predominantly non-calcareous clay of glacio-fluvial origin. Firing temperatures
ranging between 700?C and 1000?C were deduced based on mineralogical and
colour changes during firing. The colour of both the original brick and the fired
samples is consistently orange-red. This is due to the presence of dispersed hematite
formed during firing in an oxidising atmosphere from the iron-bearing minerals in
the clay. The petrography of the pointing mortar was used as an additional resource
to gather evidence for provenance. The brick temper and mortar aggregate are consistent
with each other and with the geology of the area, suggesting a local source for
both the brick-making sediment and the mortar aggregate.